Vertical smear from bright light sources? at DVinfo.net

Kevin Shaw · February 16th, 2006, 09:25 AM

Has anyone else noticed vertical smearing from bright light sources on the HD100U? Had one set up in my living room Tuesday night and was seeing dramatic vertical lines on the LCD from bright bulbs on a chandelier. Unfortunately I didn't record this to see if it came through on tape, hence why I'm wondering if anyone else has encountered this issue.

Tim Dashwood · February 16th, 2006, 10:19 AM

It is a characteristic of the densely populated pixels on the CCD, and it is normal.

Stephen L. Noe · February 16th, 2006, 11:01 AM

Quote:

Originally Posted by Kevin Shaw

Has anyone else noticed vertical smearing from bright light sources on the HD100U? Had one set up in my living room Tuesday night and was seeing dramatic vertical lines on the LCD from bright bulbs on a chandelier. Unfortunately I didn't record this to see if it came through on tape, hence why I'm wondering if anyone else has encountered this issue.

Kevin,

All HD CCD's are capable of doing this. Now that you're aware of it, you can look for it and adjust exposure down to compensate for it or reframe your shot. It's the same on the HD-100 as the Varicam in this case. They say that CMOS overcomes this but I haven't tried with a CMOS camera.

Kevin Shaw · February 16th, 2006, 09:14 PM

What concerned me is that the vertical smear on the HD100U looked dramatic in this example, but I didn't see the same effect on either the Canon XLH1 or Sony FX1 for the same scene. I'd really like to know if anyone else has noticed this being an issue for this camera compared to other HD or SD models.

Stephen L. Noe · February 16th, 2006, 09:22 PM

I have seen vertical smear and blooming on the HD-100, XL-H1, Z1 and Varicam. It's a fact of life on HD CCD's. Reframe and/or adjust exposure.

Matthew Greene · February 17th, 2006, 12:21 AM

Adjusting exposure to reduce smear is not going to work without making the shot really dark, smear happens because CCDs need to transfer each frame off of the sensor vertically. When pixels on the CCD are overloaded by a bright subject, the overload travels with the line/frame transfer.

IT CCDs are more prone to it, they're usually the ones used on lower cost cameras, other variations such as FIT CCDs have much reduced smear, usually imperceptible. Grass Valley's FT chips have no vertical smear because there's a mechanical shutter blocking the light from the CCDs during the time that the frame is transfered from the CCD. Without the shutter spinning, they would have the worst smear of any sensor.

Manufacturers sometimes offer the same camera with the only difference being an option of CCDs, the only visible difference is vertical smear although there are other very subtle differences in imaging, like FITs sometimes having a tiny amount more fixed pattern noise. For example Sony BVP-7 vs BVP-70, BVP-5 vs BVP-50. Ikegami HL-53 vs HL-55, etc... In all these cases the difference in cost between having or not having smear is in the $10,000 range.

Along with FT CCDs, CMOS sensors have no smear at all because each pixel transfers it's signal individually.

When it comes to the new HD cameras, the only one without smear would be the Sony CMOS ones. All the other cams will have it, some will be slightly stronger than others but you can point a distant bright light at any of these cameras and it will produce vertical smear.

When it comes to the Cinealta you'd have to shine an extremely bright and defined light directly at the lens (such as a high powered laser) in order to see any visible hint of smear. Sony's HAD technology lowers smear by using tiny lenses on the pixels and combined with the FIT architecture of the chips it virtually eliminates it.

The Varicam is more prone to it since it uses IT sensors, but they're engineered to reduce smear more than lower cost IT sensors. You do have to point it at the sun or at really bright light to see it. It definitely won't ruin a shot or pop out as much as in most lower cost HD cams.

Really good info on smear and different imager technologies with all their pros and cons is available in the American Cinematographer's video manual.

Ash Greyson · February 17th, 2006, 02:14 AM

What was the shutter speed? The higher you go, the worse the smear...

ash =o)

Matthew Greene · February 17th, 2006, 12:24 PM

I'm not 100% sure of the science behind that but it's probably because the smear is not generated during the light capture, it's generated during the transfer so when you have a high shutter speed the capture is quick but the CCD is exposed to light during transfer for a longer period of time than with a slower shutter speed.

Dave Ferdinand · February 17th, 2006, 02:25 PM

I found this issue to be quite annoying on my HD1.

I just did a test and changing the shutter speed doesn't seem to improve. However, changing the aperture will.

F5.6:

http://www.geocities.com/headlesspup...f/DVC00024.JPG

F22:

http://www.geocities.com/headlesspup...f/DVC00025.JPG

Not sure of the shutter speed on both but I'm assuming that it readjusts to higher at F22 and lower at F5.6.

Matthew Greene · February 17th, 2006, 07:26 PM

I'm not suggesting that you thought otherwise but some of that is not smear, it's partly a cross effect caused probably by the shape of the iris. The most obvious smear is the vertical line at the far right of the lamp.

Of course closing the iris helps since it's cutting down the amount of light that hits the sensor but in all practicality it's not a solution since you're exposing for the bulbs in lamps and not for the scene you're shooting.

February 16th, 2006, 09:25 AM	#1
Kevin Shaw Inner Circle Join Date: Sep 2004 Location: Sacramento, CA Posts: 2,488	Vertical smear from bright light sources? Has anyone else noticed vertical smearing from bright light sources on the HD100U? Had one set up in my living room Tuesday night and was seeing dramatic vertical lines on the LCD from bright bulbs on a chandelier. Unfortunately I didn't record this to see if it came through on tape, hence why I'm wondering if anyone else has encountered this issue.

February 16th, 2006, 10:19 AM	#2
Tim Dashwood Wrangler Join Date: Aug 2005 Location: Toronto, ON, Canada Posts: 3,637	It is a characteristic of the densely populated pixels on the CCD, and it is normal. __________________ Tim Dashwood

February 17th, 2006, 02:25 PM	#9
Dave Ferdinand Major Player Join Date: Jan 2005 Location: Vancouver, BC Posts: 359	I found this issue to be quite annoying on my HD1. I just did a test and changing the shutter speed doesn't seem to improve. However, changing the aperture will. F5.6: http://www.geocities.com/headlesspup...f/DVC00024.JPG F22: http://www.geocities.com/headlesspup...f/DVC00025.JPG Not sure of the shutter speed on both but I'm assuming that it readjusts to higher at F22 and lower at F5.6. __________________ Do or do not, there is no try.

February 16th, 2006, 09:14 PM	#4
Kevin Shaw Inner Circle Join Date: Sep 2004 Location: Sacramento, CA Posts: 2,488	What concerned me is that the vertical smear on the HD100U looked dramatic in this example, but I didn't see the same effect on either the Canon XLH1 or Sony FX1 for the same scene. I'd really like to know if anyone else has noticed this being an issue for this camera compared to other HD or SD models.

February 16th, 2006, 09:22 PM	#5
Stephen L. Noe Trustee Join Date: Apr 2005 Location: Chicago Posts: 1,214	I have seen vertical smear and blooming on the HD-100, XL-H1, Z1 and Varicam. It's a fact of life on HD CCD's. Reframe and/or adjust exposure.

February 17th, 2006, 12:21 AM	#6
Matthew Greene Regular Crew Join Date: Jan 2006 Location: Las Vegas, NV / Branson, MO Posts: 63	Adjusting exposure to reduce smear is not going to work without making the shot really dark, smear happens because CCDs need to transfer each frame off of the sensor vertically. When pixels on the CCD are overloaded by a bright subject, the overload travels with the line/frame transfer. IT CCDs are more prone to it, they're usually the ones used on lower cost cameras, other variations such as FIT CCDs have much reduced smear, usually imperceptible. Grass Valley's FT chips have no vertical smear because there's a mechanical shutter blocking the light from the CCDs during the time that the frame is transfered from the CCD. Without the shutter spinning, they would have the worst smear of any sensor. Manufacturers sometimes offer the same camera with the only difference being an option of CCDs, the only visible difference is vertical smear although there are other very subtle differences in imaging, like FITs sometimes having a tiny amount more fixed pattern noise. For example Sony BVP-7 vs BVP-70, BVP-5 vs BVP-50. Ikegami HL-53 vs HL-55, etc... In all these cases the difference in cost between having or not having smear is in the $10,000 range. Along with FT CCDs, CMOS sensors have no smear at all because each pixel transfers it's signal individually. When it comes to the new HD cameras, the only one without smear would be the Sony CMOS ones. All the other cams will have it, some will be slightly stronger than others but you can point a distant bright light at any of these cameras and it will produce vertical smear. When it comes to the Cinealta you'd have to shine an extremely bright and defined light directly at the lens (such as a high powered laser) in order to see any visible hint of smear. Sony's HAD technology lowers smear by using tiny lenses on the pixels and combined with the FIT architecture of the chips it virtually eliminates it. The Varicam is more prone to it since it uses IT sensors, but they're engineered to reduce smear more than lower cost IT sensors. You do have to point it at the sun or at really bright light to see it. It definitely won't ruin a shot or pop out as much as in most lower cost HD cams. Really good info on smear and different imager technologies with all their pros and cons is available in the American Cinematographer's video manual.

February 17th, 2006, 02:14 AM	#7
Ash Greyson Trustee Join Date: May 2003 Location: Tulsa, OK Posts: 1,689	What was the shutter speed? The higher you go, the worse the smear... ash =o)

February 17th, 2006, 12:24 PM	#8
Matthew Greene Regular Crew Join Date: Jan 2006 Location: Las Vegas, NV / Branson, MO Posts: 63	I'm not 100% sure of the science behind that but it's probably because the smear is not generated during the light capture, it's generated during the transfer so when you have a high shutter speed the capture is quick but the CCD is exposed to light during transfer for a longer period of time than with a slower shutter speed.

February 17th, 2006, 07:26 PM	#10
Matthew Greene Regular Crew Join Date: Jan 2006 Location: Las Vegas, NV / Branson, MO Posts: 63	I'm not suggesting that you thought otherwise but some of that is not smear, it's partly a cross effect caused probably by the shape of the iris. The most obvious smear is the vertical line at the far right of the lamp. Of course closing the iris helps since it's cutting down the amount of light that hits the sensor but in all practicality it's not a solution since you're exposing for the bulbs in lamps and not for the scene you're shooting.